<!DOCTYPE HTML>
<html>
	<head>
		<title>联通菜单</title>
		<meta charset="utf-8">
		<script>
			function change(){
				var citys=[[''],['海淀','昌平','朝阳'],['南阳','信阳','洛阳']];
				var oPro=document.getElementById('pro');
				var oCity=document.getElementById('city');
				//alert(oPro.value);
				var str=citys[oPro.value];
				for(var i=0,len=str.length;i<len;i++)
				{
					var addOpt=addOpt+'<option>'+str[i]+'</option>';
				}
				oCity.innerHTML=addOpt;
		}
		</script>
	</head>
	
	<body>
		<form method="post" action="http://www.w3school.com.cn/html5/html_5_form_attributes.asp" autocomplete="on">
		<select id="pro" onchange="change();">
			<option value="">请选择</option>
			<option value="1">北京</option>
			<option value="2">河南</option>
		</select>
		<select id="city"></select>>
		<p><input type="submit"></p>
		</form>
		
	</body>
</html>